Of the 56 million deaths reported worldwide in 2012, approximately 15 million are directly related to infectious diseases (1). The majority of annual deaths are related to bacterial infections such as tuberculosis, yellow and typhoid fever, cholera, shigellosis, pneumonia, etc. (1). Morbidity and mortality rates are highest in developing countries, where large numbers of infants and children count among the victims (2). In developed nations, infectious disease mortality falls most heavily on indigenous and disadvantaged minorities (3). The control of bacterial infectious diseases worldwide is an important task. Although antibiotics revolutionized the treatment of bacterial infections, increased resistance and the emergence of multidrug-resistant strains increasingly reduce their efficacy. This trend promotes an urgent need for better understanding of bacterial pathogenicity and resistance mechanisms, which will assist novel therapeutic and vaccination strategies.

Stages of phagosome maturation. During phagocytosis, the phagosome undergoes a series of fusion and fission events with vesicles of the endocytic pathway, culminating in the formation of the phagolysosome. Maturation of the phagosome involves gradual decrease in pH and acquisition of antimicrobial properties, leading to the digestion of the invader and presentation of antigens on the surface of the phagocyte by MHC-II molecules.

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Figure 1

Stages of phagosome maturation. During phagocytosis, the phagosome undergoes a series of fusion and fission events with vesicles of the endocytic pathway, culminating in the formation of the phagolysosome. Maturation of the phagosome involves gradual decrease in pH and acquisition of antimicrobial properties, leading to the digestion of the invader and presentation of antigens on the surface of the phagocyte by MHC-II molecules.